A Lifelong Contract binds a blade to one nervous system. Magatsumi’s contract is the master key: if Akemura dies, the other five wartime bearers die with him. Yura wanted that knot open. Then he spoke to Akemura and changed the math. Enten is the seventh and never sat in that knot.
Contracts: Lifelong Contracts. Blade: Magatsumi. Shinuchi: Shinuchi.